Manually and automatically adjustable choke for shotguns



Dec. 16, 1958 A. Y. GRAHN 2,864,194

MANUALLY AND AUTOMATICALLY ADJUSTABLE CHOKE FOR SHOTGUNS Filed Sept. 17,1957 2 Sheets-Sheet 1 l 5 INVENTOR Hrne Y. Grahn ATTORNEYS Dec. 16, 1958A. Y. GRAHN 2,864,194

MANUALLY AND AUTOMATICALLY ADJUSTABLE CHOKE FOR SHOTGUNS Filed Sept. 17,1957 2 Sheets-Sheet 2 INVENTOR Hme Y. Grahn ATTORNEYS MANUALLY ANDAUTOMATICALLY ADJUST- ABLE CHDKE F R SHOTGUNS Arne Y. Grahn, Hartford,Conn., assignor to The Poly Choke Company, Incorporated, East Hartford,(301111., a corporation of Connecticut Application September 17, 1957,Serial No. 684,583

Claims. (Cl. 42-79) This invention relates to a choke mechanism forfirearms and especially shotguns, and relates more particularly to anautomatically adjustable choke mechanism in which the adjustment of thechoke is effected by the firing or discharge of the gun. The choke isalso manually adjustable.

Adjustable choke mechanisms for firearms have long been known andautomatically adjustable choke mechanisms have been proposed, suchmechanisms usually comprising a split or slotted choke tube which isattached to the gun barrel, and a relatively movable sleeve surroundingthe choke tube and adapted to constrict it when moved upon the tube.Usually the arrangement is such that the constricting sleeve is moved insome manner in response to the firing of the gun so that automaticadjustment of the amount or degree of choke is effected.

An automatically adjustable choke mechanism has a distinct advantageover a manually adjustable type in that very often a hunter will be ableto get more than one shot at game after it has been flushed, that is,the hunter will be able to fire more rapidly owing to the automaticadjustment of the choke mechanism. Usually the first shot is made whenthe game is relatively close and no choking action or relatively littlechoking action is required. On the next shot the game is usually at agreater distance from the gun and a closer pattern of shot is,therefore, desirable. The same is true if a third shot can be firedbefore the game is out of range. If these successively closer patternsmay be effected by the choke mechanism in response to the firing of thegun more shots may be obtained at game where it would not be possible toadjust the choke manually between the consecutive discharges of thefirearm without the game getting out of range.

As previously stated, adjustable choke mechanisms usually comprise aslotted or constrictable tube and a relatively movable outer sleeve toeffect restriction of the tube. However, in the present instance aneffective choking action is obtained by means of an inexpansible choketube which is of constant diameter, that is to say, that the cylindricalwall of the tube is not interrupted by slots. Furthermore, the tube, inthe present instance, is of substantially uniform diameter exceptadjacent its rear end where it receives the charge of shot from themuzzle of the gun barrel. The diameter of the choke tube issubstantially that of the gun barrel, and choking action is obtained byvarying the distance of this tube from the nozzle of the barrel.

For example, it has been found that when the rear end of the choke tubeis close to the muzzle of the gun barrel a substantially open pattern iseffected, that is to say, almost the same pattern which might beobtained without the use of any choke mechanism. However, when the choketube is advanced a certain extent, say a half inch, away from the muzzleof the gun barrel a degree of choking action is obtained, while, if thechoke tube is moved so that its rear end is, for example, substantiallyan inch from the muzzle of the gun barrel, a

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substantially full choking effect is obtained. By making use of thisprinciple and by providing a choke tube of constant bore which may bemoved forwardly by discharge of the gun, and which is releasably held invarious adjuted positions so that it moves forwardly in a stepby-stepmanner, one step at each discharge of the gun, a reliable and efficientautomatically adjustable choking mechanism is obtained by, in effect,lengthening the gun barrel.

One object of the invention is to provide an improved automaticallyadjustable choke mechanism which very effectively chokes a shotgun andwhich is very reliable in operation.

A further object is to provide an automatically adjustable chokemechanism in which the choke tube is rotated to an extent each time thefirearm is discharged, the tube being rotated in first one direction andthen the other.

Still another object of the invention is to provide a choke mechanismhaving improved means for releasably holding the choke tube in variousadjusted positions sothat it moves forwardly in a step-by-step manner,and in which means is also provided for manually locking the tube invarious adjusted positions.

Another object is to provide releasable holding means for the choke tubewhich acts directly on the tube.

Further objects of the invention will be apparent from the followingdetailed description of one form of the choke mechanism illustrated inthe accompanying drawings by way of example.

In the drawings:

Fig. l is a side elevational view of the muzzle of a gun barrel having achoke embodying the invention ap plied thereto;

Fig. 2 is an enlarged sectional view on line 2-2 of Fig. 1 showing thechoke in open-bore position;

Fig. 3 is a view similar to Fig. 2 showing the parts in an intermediatechoke position;

Fig. 4 is a view similar to Fig. 3 but showing the parts in full-chokeposition;

Fig. 5 is a sectional view taken on line 5-5 of Fig. 2; Fig. 6 is asectional view taken on line 66 of Fig. 2; and

Fig. 7 is a fragmentary view illustrating a development of the choketube.

To illustrate an embodiment of the invention there is shown in thedrawings the muzzle of a gun barrel 10 having secured thereto bybrazing, or equivalent means, an adapter 11. Adjacent the forward endthereof the adapter 11 is provided with external screw threads formounting a cylindrical member 12 having internal threads at the rear endthereof so that it may be threadedly secured to the adapter.

As shown in Pig. 2, the internal diameter of the cylindrical member 12is somewhat greater than the bore 13 of the gun barrel and the member 12is provided with an internal annular recess 14 adjoining and forwardlyof the last-mentioned threads of the member. Adjacent the for ward endthereof the cylindrical member 12 is provided with a rearwardly facingshoulder 15 formed by internally recessing, as at 16, the bore of themember 12, this recess being of ann'ular form and providing a farwardlyfacing shoulder, as at 17. As shown in the last-mentioned view, theforwardly facing shoulder 17 is formed by an abrupt edge of the recess16 while the rearwardly facing shoulder 15 is formed by a beveled andforwardly sloping edge of the recess. A tubular choke member 18 isslidably mounted within the member 12 and the wall of the choke memberis continuous circumferentially in that it is not provided withlongitudinal slots as is usually the case in adjustable chokemechanisms. Therefore, the tubular member is of constant diameter in thesense that its diameter is not changed at any point by constriction orexpansion during use of the choke mechanism. Moreover, the diameter ofthe tubular member over the greater portion of its length issubstantially the same as that of the bore 13 of the gun barrel, At the,rear or entrance of the choke member 18;, however,'the inner wall isflared, as at 19, sov as to provide a funnel-shaped portion to receivethe charge of shot from the'rnuz zle of the gun barrel. choke member 18may be slightly spaced forwardly a distance of /3 of an inch or morefrom the muzzle of the gun barrel in the position of Fig. 2, the chargeof shot It will be appreciated that as the rear of the 4 track 26 isprovided with extensions 28, 29 for a purpose which will appearhereinafter.

The automatic operation of the choke mechanism is as follows. When theparts of the choke mechanism are in the open-bore position of Fig. 2 andthe stop pin 25 is located in the track in the broken-line (see Fig. 7)position indicated at 30, subsequent discharge of the gun effectsmovement of the stop pin 25 relatively to the may expand slightly beforeit reaches the member 18. i

The flared portion 19'of the choke member recollects the shot anddirects it into the portion of the member which is of substantially thesame diameter as the bore 13 of the gun barrel.

A split ring 29 embraces the choke member 13 and extends into theinternal annular recess 16 formed in the cylindrical member 12, thewidth of the ring being substantially that of the recess. The ring 20'is held against appreciable movement inthe recess by contact of itsabrupt rear edge with the abrupt forwardly facing shoulder 17, and bycontact of the rearwardly facing and beveled shoulder cooperating withthe forward and beveled edge 21 of the ring. The split ring 28 fits,with a suitable amount of friction, about. the outside diameter of thetubular member 13 and, as the ring is held against axial movement withinthe cylindrical member 12, it inhibits relative movement between thelatter and the choke member. When the choke member 18 is moved'forwardlyby the discharge of the gun, as will appear hereinafter, there is atendency for the ring to move forwardly and contact the beveled surface15 of the cylindrical member 12, and this contact tends to constrict thering about the choke member so as to exert the required friction uponthe latter. It will be manifest that it is desirable not to havethechokemember moved throughout its full choking range by a singledischarge of the gun, but to have it move in a step-by-step manner andto this end a locking means is provided to releasably hold the chokemember at various positions of adjustment axially of the gun barrel aswill appear hereinafter.

An outer cylindrical or sleeve member 23 embraces the cylindrical member12, the member 23 having a cylindrical side wall structure providingclearance with the cylindrical side wall structure of the member 12. Asshown in Fig. 2,'the sleeve member 23 is shorter than the cylindricalmember 12 and at its outer end is provided with an inwardly extendingcircumferential flange 24, the flange being threadedly secured toexternal threads formed at the forward end of the tubular choke member18. Thus it will be understood that the tubular choke member is, inelfect, integral with the outer sleeve member 23 and in its movementscarries the member 23 with it.'

Hence the members 18 and 23, when secured together, may be referred toas the choke tube.

To releasably hold the choke tube in positions of adjustment axially ofthe gun barrel either the choke tube or the cylindrical member 12 isprovided with a fixed stop member. In the form illustrated in thedrawings, the stop member, indicated at 25, is provided on thecylindrical member 12 and cooperates with a track which, in thisinstance, is formed, not on the sleeve member 23 as it might be, but onthe tubular choke member 18, the track being indicated at 26. As shownin Fig. 2, the fixed stop member 25 is formed by a radially inwardlyextending headed pin at the forward extremity of. the cylindrical member12 and received in the side wall struc-- ture thereof. The track 26 isgenerally of zigzag or V shape (see Fig. 2), the arms thereof beingcurved outwardly somewhat from the apex of the V. In the instant formthe track 26 is formed by grooving the external surface of the tubularmember 18. The grooved choke tube so that the pin travels along thetrack 26 until stopped by the latter in the broken-line position 31shown in the last-mentioned view. This movement is effected by theoutward propulsion of the choke tube, prob ably due to the impact of theshot as it is gathered in the collection portion 19 of the tube. It willbe understood that during this movement of the choke tube the tube isrotated to some extent due to the direction of the track 26. It willalso beunderstood that the split ring 20 serves to frictionally restrainthe outward movement of the choke tube. Due at leastin part to themomentum of the rotarymovement of the choke tube the stop pin 25 travelsdown one arm of the V-shaped track but does not travel along the otherarm of the track until the gun is discharged a second time. It will beunderstood that when the stop pin 25 comes to rest in the last-mentionedposition the choke tube is in the intermediate position of Fig. 3 andsubsequentdischarge of the gun effects further move.- ment of the stoppin 25 relatively to the track 26 so that the pin 25 travels along saidother arm of the V-shaped track' 26 coming to rest in the broken-lineposition (see Fig. 7) indicated at 32. As the pin travels along thetrack 26 to. the last-mentioned position thereof, the choke tube isrotated in the other direction. A third shot may be fired in thisposition of the choke parts and it will be understood that when theparts are in this, the full-choke, position (Fig. 4)- further chokingaction is prevented by engagement of the stop pin 25 with the innerterminalof the track 26. Thus it will be'understood that the choke tubeis moved from the open-bore position of Fig. 2 to the full-chokeposition of Fig. 4 in a step-by-step manner and it will befurtherunderstood that, if desired, additional outward adjustments of the choketube may be effected by providing a longer zigzag track for the stop pin25 instead of a V-shaped track. As shown in Fig. 4, the outer surface ofthe cylindrical member 12 may be provided with indicia cooperating withthe rear edge of sleeve 23 to give a visual indication of the, degree ofchoke.

. The choke tube may be manually adjusted and may be locked in eitherthe open-bore or intermediate choke positions. This may be done bymanipulation of the sleeve member 23. For example, when the stop pin 25is in the open-bore position 30 indicated in Fig. 7, the sleeve member23; may be grasped and rotated to move the pin 25 relatively to thechoke tube so that the pin enters and engages in the extension 28 of thetrack. When the stop pin 25 is in the last-mentioned position, the choketube is effectively held against axial movement when the gun issubsequently fired. When the choke mechanism is in the open-boreposition rearward movement of the choke tube is prevented by engagementof the flange 24 with the front end of the cylindrical member 12. Whenit is'desired" to lock the pin 25 in the intermediate choke position,the choke tube may be rotatedto move the pin 25 relatively to the'choketube so that the pin moves from the position 31 shown in Fig. 7 to aposition in the extension 29, of the track. It will be understoodthatwhen the pin 25 is engaged in the extension 29 subsequent dischargeof the gun does not etfect outward movement of the choke'tube. As shownin Fig. 7, the extension 29' is slightly offset from'the' maticadjustment, that is, when the pin 25 is in the positi'on 30, indicatedin Fig. 7, prior to discharge of the gun.

It will be further understood that the choking effect of the mechanismin any given position thereof will vary in accordance with the diameterof the tubular member 18, and that while the member 18 is indicated inthe drawings to be of substantially the same diameter as the bore 13 ofthe gun barrel, the internal diameter of the tubular member 18 at theforward end thereof may be somewhat greater or less than the diameter ofthe bore 13, if desired.

One advantage of the choke mechanism resides in the provision of the pinand track means constituting the releasable lock for holding the choketube in its automatically adjusted positions. The pin and track meansreduces friction in the releasable lock to a minimum. Furthermore, thereis provided means for preventing automatic adjustment of the choke tubeand for locking the latter manually in various adjusted positions. Itwill be appreciated that in the form shown the releasable locking meansfor holding the choke tube in either its manually or automaticallyadjusted positions is interposed between the fixed cylindrical memberand the inner choke member, the locking means acting directly on thelatter. Still further, it will be understood that owing to the provisionof the track on the outer surface of the inner choke member the entranceof dirt or other foreign matter into the track is effectively inhibited.In this connection it may be noted that the outer sleeve member 23extends over all portions 'of the track, as shown in Fig. 4. It will bemanifest from the foregoing disclosure that there is provided animproved choke mechanism constituted by few and simple parts and whichis very reliable in operation.

While only one form of the choke mechanism has been shown in thedrawings and described above, it will be apparent that the chokemechanism may take other forms and is susceptible of various changes indetails without departing from the principles of the invention and thescope of the appended claims.

What I claim is:

1. A choke mechanism for a gun barrel comprising a hollow cylindricalmember extending forwardly from the muzzle of the gun barrel in fixedrelation thereto, a choke member comprising a tubular charge-chokingelement extending into and slidable in said cylindrical member forforward propulsion by impact on said element of a charge fired from thegun, and cooperating interengaging means on said members for effecting astep-by-step forward movement of the tubular element on discharge of thegun, said mean comprising a zigzag track on one of the memberscooperating with a stop element fixed to the other member and relativelymovable along the track, so that the choke member is rotated in firstone direction and then the other as it is advanced.

2. A choke mechanism for a gun barrel comprising a hollow cylindricalmember extending forwardly from the muzzle of the gun barrel in fixedrelation thereto, a choke member comprising a charge-choking tubularelement extending into and forwardly slidable insaid member, for forwardpropulsion by impact on said element of a charge fired from the gun, thechoke member having a sleeve element embracing the cylindrical memberand rigid with the tubular element at the forward end of the latter soas to be slidable therewith, one of said elements having a zigzag trackformed thereon and facing the cylindrical member, said cylindricalmember having a stop pin fixed thereto and relatively movable along thetrack, so that the tubular element is rotated in first one direction andthen the other as it is advanced, for effecting a step-by-step movementof the tubular element on discharge of the gun.

3. A choke mechanism for a gun barrel comprising a fixed element havinga tubular part extending forwardly from the muzzle of the gun barrel, achoke tube having a first and charge-choking tubular part extending intoand forwardly slidable in said part of the fixed element, for forwardpropulsion by impact thereon of a charge fired from the gun, said choketube having a second tubular part embracing said part of the fixedelement and rigid with said first tubular part at the forward end of thelatter so as to be slidable therewith, and cooperating interengagingmeans between one of said tubular parts of the choke tube and saidtubular part of the fixed element, for effecting a step-by-step forwardmovement of the choke tube on discharge of the gun, said meanscomprising a stop element fixed on one of the two last-mentioned tubularparts and a zigzag track on the other, the stop element being relativelymovable along the track so that the choke tube is rotated in first onedirection and then the other as it is advanced.

4. A choke mechanism for a gun barrel comprising a fixed member having acylindrical part extending forwardly from the muzzle of the gun barrel,a choke tube having a charge-choking tubular part extending into andforwardly slidable in the cylindrical part, for forward propulsion byimpact on said tubular part of a charge fired from the gun, andcooperating interengaging means on said member and choke tube torestrain forward movement of the tubular part and to rotate the latterfirst in one direction and then the other so that the tubular part isadvanced in a step-by-step manner.

5. A choke mechanism for a gun barrel comprising a fixed member having acylindrical part extending forwardly from the muzzle of the gun barrel,a choke tube having a charge-choking tubular part extending into andforwardly slidable in the cylindrical part, for forward propulsion byimpact on said tubular part of a charge fired from the gun, andcooperating interengaging means on said member and choke tube torestrain forward movement of the tubular part and to rotate the latterfirst in one direction and then the other so that the tubular part isadvanced in a step-by-step manner, said means acting directly on saidtubular part.

6. A choke mechanism for a gun barrel comprising a fixed member having acylindrical part extending forwardly from the muzzle of the gun barrel,a choke tube having a charge-choking tubular part extending into andforwardly slidable in the cylindrical part, for forward propulsion byimpact on said tubular part of a charge fired from the gun, andcooperating interengaging means on said member and choke tube torestrain forward movement of the tubular part and to rotate the latterfirst in one direction and then the other so that the tubular part isadvanced in a step-by-step manner, said means acting directly on saidtubular part and comprising a V-shaped track on one of said partscooperating with a stop pin fixed to the other part.

7. A choke mechanism as defined by claim 6, wherein said means includesa split ring carried by one of the parts and bearing against the otherto restrain forward movement of the tubular part.

8. A choke mechanism as defined in claim 7, wherein at the distal end ofthe forward arm of the V the track is provided with an offset extensionso that the stop pin may be manually locked therein to prevent forwardpropulsion of the tubular part on discharge of the gun, the track beingprovided with a second pin-locking extension adjacent the apex of theV-shaped track.

9. A choke mechanism as defined by claim 8, wherein the track is formedby a groove in the outer cylindrical surface of the tubular part and thestop pin is fixed to and extends radially inwardly from the cylindricalpart, the choke tube having a second tubular part of a length to extendover the track and embracing the cylindrical part in fixed relation tothe first tubular part.

10. A choke mechanism comprising a cylindrical member adapted to besecured to the muzzle of a gun barrel, a choke tube comprising acharge-choking tubular member extending into and forwardly slidable inthe cylindrical member, for forward propulsion by impact on T saidtubular member of a charge fired from the gun, the choke tube having asleeve member embracing the cylindrical member and rigid with theforward end of the tubular member so as to be carried thereby, andcooperating interengaging means on the cylindrical member and the choketube providing various positions in which the choke tube may be,manually and selectively locked against propulsion by discharge of thegun, and also providing for self-propulsion of the tube through a rotarymovement of the latter in a step-bystep manner.

References (Iited in the file of this patent UNITED STATES PATENTS2,270,592 Kitzrniller Ian. 20, 1942 2,428,232 Limon Sept. 30, 19472,731,754 Gibson Jan. 24, 1956 2,759,286 Moore Aug. 21, 1956

